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W. P. DAVEY LECTROSTATC VOLTMETER Aug.- 25., 1925.

Filed Aug.'

miga@ lill Inventor'. Whe eLerE Daveytial, together with suitable housing and Patented Aug. 25, 1925.

1 UNITED-STATES COMPANY, yA.CORPORATION QENEWYOE'K..

Ermorno's'ria'lrc VOLTMETEE.

Apt'natiovied ,august 242719223.' L'serial naesazs's." K'

" To alll whom t may concern.'

. Be it known that'I, VHEELER P.' DAvEY. a citizen of the United States, residing at Schenectady, the county of Schenectady, State ot New York, have invented certain new and useful Improvements vin Electrostatic Voltmeters, of which the following is a specication. y j

My invention relates to electrostatic voltmeters and has for its object the provision ot' a! simple and inexpensive instrument of its class capable of measuring high potentials of either direct or alternating Ycurrent with accuracy. 'In vcarrying-my invention' yinto eti'ect, I provide cooperating movable and stationary elements arranged to be subjected simultaneously to the potential under investigation and to create by means of are- Vvpulsive action between them, al movement which is proportional to the applied potenmeans for 'indicating the extent of movement. i

` The features otfmy invention which I believe to be novel and 'patentable will be pointed out in' the claims appended hereto. A preferred modification of my invention will now be Vdescribedfin connection with/the accompanying 'drawings in' which Fig. 1 representsr a vertical cross section through an instrument builtin accordance with my invention; Fig. 2 ar horizontal section taken on lline 2-2 of Fig. 1; Fig. 3 a horizontal section takenv on line 3-3 of Fig. 1, and Fig. 4 an exterior view of the indicating part ot the instrument. Referring to the drawings, in which like parts. are designated by like `numerals throughout, 10 indicates a suitable cylindrical tank provided with a cover 11 of insulating material such as wood, liber or hard rubber. The tank is preferably provided with leveling screws 12. The tank 10 contains an insulating fluid such as oil and is provided with suitable bailes 13, 14

and 15 to prevent disturbing circulating currents in the insulating fluid. Vertically supported by the cover 11 is a relatively thick cylinder 16 preferably made of woodk or other suitable material extending into the oil tank and abovethe cover. A brass tube 17 ts snugly within the wooden cylinder 16 and is provided with threaded ends adjacent the ends of cylinder 16. On the lower end of tube 17 and immersed in the insulating oil contained within tank 10 is secured afmetallic cross piece 1,8 which abuts lagainst il' the lower end vof 'cylinder'ldy 'This' cross piece supports two vertical, Vstationary electrodes 19 vand 2Q equally spaced with' respect tothe centerline of the apparatus.;k Af'supporting'cross piece`21 joins 'the lowerfends of the-two electrodes. The' cross piece'21 and the electrodes19and 20 'are Agiven' the forlnshow'n'in ig. y2 and are made of conducting material, such as brass. i

n VrIo the top of tube 17V is secured ametallic .cap 22 securely holding the tube 17 andcylinder"16 together. This'cap isprovidedwith aterminal `23 for attaching'the conductor which isjsubjected t0 'the' potential, tol be measured; Y u f j Torsionally suspended within tube'17' by means of a central wire 24is a smaller tube '25 preferably made of brass. Thewire 24 is secured in suitable clamps 26 and 27'in-cap 22and on cross piece 21 respectively. Tube 25 isv rigidly lsecuredto the. torsional wire only near its center by means of a suitable clamp 28."v The tube 25and the parts carried thereby are held in proper alinement by 'guides 29 and 30' in thetop and bottom-'ends respectively ofthe Vtube 25.1"-'1hetors'ional wire24 r'i'ass'es'rv freely through these guides. Within 'the oil chamber f and 1 adj acent-fy the stationarylelectrode, .n tube 25 carries laV lpair of electrodes31` and 32 secured-to theltube by means of arm 33 and bushing 34 all made of conducting material, such as brass.

The torsional system is initially adjusted so that the movable and stationary electrodes vstand in the relation shown in full lines in Fig. 2. Near the top of the instrument, cylinder 16 and tube 17 have portions cut away as indicated in Fig. 4 in order that an indicating device hereV illustrated as a mirror 35, attached to cylinder 25, may be seen and any torsional movement of the system indicated. When a mirror is used as the indicating device, the well known method of. refiecting a beam of light on to a suitable stationary scale will be utilized. It a pointer is used, it will be attached to the cylinder 25 in place of, o-r in laddition to, the mirror and will cooperate directly with a suitable stationary scale, not shown.

by since both are electrically connected to terminal 23 through the metallic part-s of the instrument It will thus be evident that when potential is applied, a repelling force will be set up between the movable and stationary electrodes, which force will be increased as the applied potential is increased, causing a substantially proportional torsional movement of the system as indicated in. dotted lines in Fig. 2. A corresponding deflection o-f the indicating device which is rigidly attached to the movable electrode will result. Y

All parts of the instrument subjected to the applied potential are surrounded by liberally curved surfaces so that corona discharges are minimized. All interior parts of the instrument are subjected to the same potential so that there is no need of insulating various circuits from each other. After the device is yadjusted and calibrated, the operator need not touch the instrument and consequently there is little danger from eX- posure to high potentials. When it is desired to measure the potential between two circuits, one line is attached to the case and the other to the terminal 23. For measuring potentials above ground, the case will be grounded.

I have found that this instrument will measure either alterna-ting current or direct current potentials between 25 and 100 kilov volts with an error not exceeding 125 volts.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention, together with the apparatus which now consider to represent the best embodiment thereof, but I desire to'have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other What I claim as new and desire to secure by Letters Patent of the United States, is

l. An electrostatic voltmeter comprising a tank, an insulating fluid in said tank, a pair of diametrically disposed electrodes immersed in said fluid, a vertical tube centrally disposed with respect to said electrodes, an electric terminal on the upper end of said tube exterior of said tank, said tube being connected tosaid electrodes, a pair of movable electrodes torsionally suspended on the center line of said tube and cooperating with said stationary electrodes, a torsional suspension passing through said tube and electrically connecting said movable electrodes with said terminal and an indicator rigidly attached with said movable electrodes and mounted above said tank for indicating the position of said movable electrode.

2. In a measuring instrument, al vertically, torsionally suspended movable element adapted to be subjected to high potentials and to have a portion thereof immersed in an insulating fluid comprising a torsional wire, a tube of sufficient diameter to prevent excessive corona discharges when subjected to high potential surrounding said wire and rigidly secured thereto near its center, guides carried in the end of said tube through which said wire freely passes, a movable electrode rigidly secured to the lower portion of said tube and an indicating element rigidly secured to the upper portion of said tube- In witness whereof, l have hereunto set my hand this 23rd day of August, 1923.

WHEELER P. DAVEY.. 

